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4.510 Digital Design Fabrication
Fall 2008
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4.510
Design Fabrication
Department of Architecture
Massachusetts Institute of Techonology
Assignment 3
Sept 28, 2008
Design and Fabrication of a Plywood Chair
Prof. Larry Sass
This assignment is due in class and posted on Stellar, Monday, October 21 2PM
Figure 1. Prototyping & redesign of a chair designed by Noel Davis (left) at TU Delft, Holland
Courtesy of Noel Davis. Used with permission.
1.0
Design Problem
Now that you have experienced prototyping in class it is time to redesign and fabricate a new chair for
posting and publishing on the web. Your group is required to redesign the “Noel Davis” chair, improve
upon its looks, function or structure in order to fabricate a completely new chair from one sheet of 4’ x 8’ x
½” (remember it is not a true ½”) plywood. The new chair should be a work of art in appearance and
function. In essence it should follow the Vitruvian design concepts of “strength, utility and aesthetic effect”,
later translated to “firmness, commodity and delight” by Sir Henry Wotton (1568-1639). The challenge is
tougher than most think, today there are many chairs on the market, exciting, fun to sit in and see. There
are few chairs that look, feel and function well at a low price point. Here is your chance to change the
world of chair design. Try to re-design the existng chair or design a new chair with a specific use. Your
chair should strive to be high end.
Assignment Criteria
- Product
A chair (not a sofa)
- Material
Baltic birch plywood
- Assembly
Friction fit (no screws or secondary attachments)
- Tool
CNC router
4.510
Design Fabrication
Department of Architecture Massachusetts Institute of Techonology 1.0
Items included in this assignment
AutoCAD DWG: A chair designed by Noel Davis – See thesis on Dspace.mit.edu
PDF: On making chairs comfortable: How to fit the seat to the sitter, Alan Marks, Fine Woodworking #31,
Nov ‘81
PDF: On designing chairs: how to develope ideas into woodworking drawings, Alan Marks, Fine
Woodworking
2.0
Recommended Schedule
September 28
Assignment Posted/Cut a Demo Chair on the router – see enclosed files
Read the articles
October 6
In class design discussion/ Design or redesign chair in CAD
October 13
Build Prototypes/Prep for CNC
October 21 Turnin
3.0
Engineering the Design There are three basic areas to study, (1) appearance or shape, (2) structural makeup as components, (3) and assembly. 3.1
Design for Shape& Chair Function First, build a design prototype of your new proposal as a solid model in CAD (Rhino, AutoCAD, etc) then
on the rapid prototyping machine. One chair does not fit all be sure to define the audience, range of users and purposes. For example, A child’s high chair. Remember you must design for fabrication as well- you are provided only one board of plywood and it is flat (hard to bend into curves). 90 Degrees
Chair ergonomics
7 Degree pitch
Settling back in chair
Comfort
Figure by MIT OpenCourseWare.
4.510
Design Fabrication
Department of Architecture
Massachusetts Institute of Techonology
3.2
Design for Structure
A highly complex function in the design process will be balancing structure and shape. Some chairs are
similar in structure to a post and beam building systems. Here posts (the legs) can be 1” in width (p),
default material thickness is ½”(t) and spacing between components can be 2” or less (k). An important
design challenge is to design the chair for serious loading and random deflection always keeping in mind
that only 3 legs are on the ground at any given time.
k
t
p
Deflection
Diagonal bracing
Bending
Figure by MIT OpenCourseWare.
3.3
Design for Assembly
Last, integrate joining techniques between components into the structure and shape. Joining and
assembly should not be considered the last step in design, it is as important as the shape. Four joining
methods are offered below they should serve as a starting point or design your own signature joinery if
necessary.
Bi-Lateral
Running
Edge
Knot
Figure by MIT OpenCourseWare.
4.510 Design Fabrication Department of Architecture Massachusetts Institute of Techonology 4.0
Model Organization and Fabrication
The best designs are based on choices offered the designer and user, thus great designs are an
amalgamation of best choices and real world testing. In order to generate and test many good and bad
concepts, physical prototyping becomes a critical component in the workflow. Organization of the model
and modeling techniques can make for a fast and efficient design production system that allows the
designer to generate design variations. Results of an efficient process are physical models with a lot of
variation between each scheme. Rule of thumb is one new design per day. Below is a fundamental
workflow for digital fabrication use it to guide you through the design and fabrication of your chair.
a) Design Model – Build solid shapes do not worry about materials here,
focus on chair appearance, style and functions. Build the chair at full
scale in CAD (1’ = 1’-0”). You may want to build more than one model and
discuss them within your group. A model should not take more than 1
hour to generate.
b) Material and Structure Model – Translate solid geometries to
surfaces of ½” thickness, find solid areas while questioning structure. At
this stage a prototype model is best, cut on the laser cutter of 1/8”
plywood then glue at the assemblies. Do not fear redesign at this stage,
outcomes of the first prototype may not be as expected.
c) Construction Model – Reduce surfaces to efficient components with
butted connection points. Next, assign predetermined joineries to abutting
components or create new joineries as needed
d) Cut Sheet – Translate 3d components to 2d positions and number
accordingly. It is also possible to label each component with symbols.
Numbers must be geometric not typical CAD numbering (explanation in
class).
e) CNC design – Optimize part organization within a 4’ x 5’ sheet of
plywood. Make sure that all geometries are closed paths.
4.510
Design Fabrication
Department of Architecture Massachusetts Institute of Techonology 4.0
In Class Presentation
Bring the chair to class on November 22 grading is based on the follow:
1.
2.
3.
4.
5.
Structure
Assembly
Visual appeal
Fabrication efficiency
Comfort
15%
15%
20%
20%
20%
Present the process with no more than 10 power-point slides
5.0
TURNING IN PROCEDURE FOR STELLAR
UPLOAD:
PDF
October 21 @ 2PM
a.
Name, Date, Assignment #
b.
Image of Design Model (Axonometric View)
c.
Image of Construction Model (Axonometric View)
d.
Digital Photo of final figure
e.
10 Page max
CLASS TURN IN:
Printout PDF – turn in at the end of class
PLACE:
Around the Dome